1. Technical Field
The present invention relates to a subprogram which performs a predetermined process in response to a call from a main program and returns the result of the process to the main program.
2. Related Art
There has been conventionally known a subprogram, such as a plug-in, which performs a predetermined process in response to a call from a main program and returns the result of the process to the main program.
The result of the process returned from the subprogram to the main program may include such data as may cause a problem if used in an unauthorized manner, such as access right information related to restriction of use, unpublicized information, or a decryption key.
There is known an attack of spoofing the main program when such data with high confidentiality is handed from the subprogram to the main program. As such an attack, there is an attack of falsifying the main program itself or an attack of intruding between the main program and the subprogram to sniff or falsify data exchanged between them.